The purpose of this study is to investigate three aspects of the growth and biology of human colon carcinoma and to attempt to relate them to each other and to the clinical extent and course of the disease. The areas to be investigated include the following: (1) the release of circulating antigen by the tumor, as a potential mechanism of escape from immunologic control. (2) Elaboration of proteolytic enzymes by primary and metastatic colon carcinoma as a mechanism in the development of metastases. (3) Tissue levels of cyclic AMP, cyclic GMP, and cyclic CMP in normal colon mucosa, primary carcinoma and metastatic carcinoma, as factors in general tumor activity and growth control. Clinical information including location and extent of primary tumor, presence of regional lymph node metastases, and presence of distal metastases, will be obtained at the time of surgery. Followup of the patients for recurrence of their disease will be carried out over a period of three or more years.